Open the cupboard under your kitchen or bathroom sink and you've found one of the most reliable pest hotspots in any Sydney home. It's dark, it's often damp, pipes pass through it, and it's rarely disturbed—everything a pest wants in one small space.
If you keep finding cockroaches, ants, or silverfish under the sink, the cupboard itself is telling you why. Here's what's drawing them and how to turn it from a pest magnet into a dead zone.
The core issue: Under-sink cupboards combine the three things pests need—moisture (leaks, condensation), shelter (dark and undisturbed), and entry (gaps around pipes). Fix those three and the pests lose their reason to be there.
Why Pests Love the Under-Sink Cupboard
- Moisture: Slow leaks, condensation on cold pipes, and damp from the waste trap—the biggest draw of all.
- Pipe penetrations: Gaps where water and waste pipes enter are open doorways from wall cavities and the subfloor.
- Darkness and quiet: Rarely opened, cluttered with bottles—ideal undisturbed harbourage.
- Warmth: Close to appliances and hot-water pipes.
- Food residue: Bin liners, recycling, and cleaning cloths leave traces pests feed on.
Which Pests You'll Find There
Cockroaches
The classic under-sink pest. German cockroaches in particular love the warm, damp, hidden conditions and breed in the gaps and clutter. 👉 How to Get Rid of Cockroaches
Ants
Ants follow moisture and food, and the pipe gaps give them a direct trail in. 👉 Sugar Ants in the Kitchen
Silverfish
Damp, dark cupboards are prime silverfish territory, especially in bathrooms. 👉 Silverfish in Sydney Bathrooms
Drain Flies
If the waste pipe or an adjacent drain has a buildup, drain flies can breed nearby. 👉 Drain Fly Infestations
Step 1: Fix the Moisture
This is the single most important step—remove the water and most pests lose interest.
- Check for leaks at the tap connections, waste trap, and pipe joints—fix even slow drips.
- Dry out the cupboard completely and check for swollen or water-stained chipboard.
- Wrap or insulate cold pipes that sweat with condensation.
- Improve ventilation—leave the cupboard open to air out periodically.
- Check the floor of the cupboard for soft spots that signal ongoing damp.
Step 2: Seal the Entry Points
- Seal the gaps around water and waste pipes where they enter the cupboard with sealant or steel wool plus sealant.
- Fill cracks at the back and base of the cupboard.
- Check where the cupboard meets the wall and floor.
- Fit covers to any unused pipe penetrations.
👉 More on sealing: Seasonal Pest-Proofing Maintenance.
Step 3: Clean and Declutter
- Empty the cupboard and give it a thorough clean.
- Reduce clutter—fewer bottles and bags means fewer hiding spots.
- Store items in sealed plastic tubs rather than loose or in cardboard.
- Keep bin liners and recycling clean; rinse before storing.
- Don't store damp cloths or sponges in the cupboard.
- Wipe it out regularly so residue doesn't build up.
Step 4: Treat (Carefully) Around Food Areas
The under-sink cupboard is near food and dishes, so be cautious with chemicals:
- Gel baits placed in the back corners target cockroaches and ants without spraying surfaces.
- Avoid heavy spraying inside a cupboard that stores cleaning items used near food.
- For German cockroaches, baiting beats spraying—and a professional is usually needed to clear them.
👉 Related: Keeping Pests Out of Your Kitchen in Summer.
When to Call a Professional
- German cockroaches under the sink—they breed fast and resist retail products.
- Pests keep returning despite fixing moisture and sealing gaps—there may be a nest in the wall or subfloor.
- You suspect a hidden leak feeding the problem inside the cabinetry or wall.
- Activity spreading to other cupboards or rooms.
👉 Read When to Call Professional Pest Control.
Final Thoughts
The under-sink cupboard is a pest magnet because it quietly offers moisture, shelter, and entry all at once. The fix follows the same order every time: kill the moisture, seal the pipe gaps, declutter and clean, then bait carefully if needed.
Sort those out and the cupboard stops being an invitation. If pests keep coming back—especially cockroaches—there's likely a hidden source, and that's the point to call a professional.
👉 Persistent under-sink pests? Pest Control Sydney Wide